In orthodontia steel wires of the kind in question are applied in such manner as to insert them under bias in so-called band fasteners which in turn are welded on to rigid bands, preferably steel bands. The steel bands are adapted accurately to the tooth to be regulated and cemented to the same so as to exert a constant directed action of force on the tooth. Initially it was preferred to bend steel wires of circular cross section. Yet that did not permit sufficiently firm fixation of the bend in the band fasteners. Particularly, it was not possible with wires having a circular cross section to transmit a torque about the longitudinal axis of the wire to the band fastener or to the tooth. Therefore, the general practice went over to forming the bends from square wires. Thus accurate fitting of the square bend in the respective band fastener can be obtained and from the bend a torque about the longitudinal wire axis can be transmitted to the fastener, the band, and thus to the respective tooth. Transmission of the torsional moment may be effected either by twisting the square wire with such aim when producing the bend that a respective restoring moment will result upon insertion in the fasteners provided. In this case fasteners having their square recesses oriented in the same way can be used for all bands. Yet it is also possible to transmit a torsional moment by not pre-twisting the square wire anywhere but instead giving the square recesses in the fasteners different inclinations in accordance with the desired moment to be transmitted to the tooth. In both cases the effect obtained is the same, namely that the bend is biased by a torsional moment at the location of its connection to the band fastener and that the moment of reaction thereof is transmitted to the tooth.
When making the bends which must be formed by hand by the orthodontist himself for each individual case, it is particularly difficult to obtain exactly the desired torsion of the square wire or, when using fasteners with differently inclined recesses, to avoid any twisting at all of the square wire since an undesired twist in the square wire would cause a wrong action of force on the respective tooth. The situation is especially serious because a permanent torsion of the square wire once made cannot be undone, which means that a single error made in curving the bend makes it necessary to discard the bend as waste. So far it has been attempted to avoid any such bending errors by developing special loop bending pliers. These pliers are of very intricate shape and thus very complicated to produce with all the corresponding high costs. Although the problem explained above of avoiding undesired twisting of the square wire has been known for many years, perhaps even for decades, and although attempts have been made for the same length of time to solve the problem by correspondingly designed special pliers, it has not been possible to provide a tool which would enable the orthodontist to make the bends in question without difficulty. Rather, it showed that even when using very expensive special pliers, the production of exactly the desired shape of the bend was more or less a question of luck.